Chlorine dioxide production

ABSTRACT

A process for the manufacture of chlorine dioxide by the reaction of a non-oxidizable acid with chlorate and a chloride in the presence of a catalyst which is an ammonium salt.

United States Patent 1 Sims et a1.

[ CHLORINE DIOXIDE PRODUCTION [75] Inventors: Leslie L. Sims, Mobile, Ala.; Walter W.'Lawrence, Jr., Baton Rouge, La.

[73] Assignee: Ethyl Corporation, New York, NY.

[22] Filed: Oct. 31, 1972 [211 App]. No.: 302,485

Related U.S. Application Data [63] Continuationimpart of Ser. No. 55,581, July 16,

1970, abandoned.

UNITED STATES PATENTS 2,736,636 2/1956 Day et a1. 423/479 Oct. 9, 1973 Rapson 423/478 Partridge et al. 423/478 FOREIGN PATENTS OR APPLICATIONS 597,199 1/1948 Great Britain 423/478 Primary ExaminerEdward Stern Attorney-Donald L. Johnson et a1.

[5 7 ABSTRACT A process for the manufacture of chlorine dioxide by the reaction of a non-oxidizable acid with chlorate and a chloride in the presence of a catalyst which is an ammonium salt.

6 Claims, No. Drawings I CHLORINE DIOXIDE PRODUCTION CROSS REFERENCE TO RELATEDAPPLICATION This application is a continuation-in-partof applic'ation Ser. No. 55,581, filed July 16, 1970, now abandoned.

BACKGROUND OF THE INVENTION SUMMARY OF THE INVENTION The present invention provides a process forthe" manufacture of chlorine dioxide bythe reaction ofia non-oxidizable acid with a chlorate and a chloride, the improvement comprising carrying out the reaction in' the presence of a-catalyst selected'from the group-con sisting of ammonium salts.

DESCRIPTION OF THEPREFERRED EMBODIMENTS In the process of the presentinvention'the chlorate and the chloride'are dissolved in anon-oxidizable'acid to produce the following reaction: 1

Representative acids which are'suitable'include, for example, sulfuric, fluosilicic, phosphoric,.perchloric, hydrofluoric, i.e., any strong acid containing an-anion-not subject to reactions eitherwithchlorine'or chlorine di oxide and which is reasonably stable.

Unfortunately, with the use of theabove acids'-,it*is frequently difficult to suppress the formation of chlorine rather than chlorine dioxide. The present invcntion provides a process whereby the production of chlorine is suppressed and the yieldof chlorine dioxide is increased byutilizationof a catalyst: 'Amongthe cat alysts which may be employed, ammoniumsulfateis preferred because of its availability and particularly excellent results, but'other ammonium salts are'suitable,

such as ammoniumnitrate, ammonium chloride, ,am-' monium fluoride, and the like.

The reaction in the presence of oneof the catalysts is suitably carried out at a temperature -in the range of from to about 150 C and preferably from about'50 to about 125 C. Especially suitable are catalyst-con centrations of from about 0.1 to about grams perliter of catalyst in reaction solution.- Concentrations outside these ranges-may be employed; though with'not as good results. I q

The chlorate and chloride are used in'substantially stoichiometric quantities and are preferably present in the reactor at concentrations below about 0.5"molar'.

More preferably, the concentrationsof chlorateand chloride are maintained below'about 0.1 molar.

tion chloric and hydrochloric acids. Chlorides and chlorates of metals capable of exhibiting stable monoor divalency are suitable,such as the alkali and alkaline earth metals, cadmium, lead, nickel, copper, cobalt, zinc and silver. I

Chlorine and chlorine dioxide are gases at ordinary temperatures and have limited'solubility in water, and therefore they are removed from the reactor solution by an inert gas stream or by maintaining the reactor Although sodium chloride and sodium-chlorate are I preferred, amongother reasons becauseof the relatively low cost of these salts, other cations-thansodiurn under vacuum. Of course, continuous removal of such gaseous reaction products causes the reactions forming them to proceed efficiently whereby the chlorate and chloride in the reactor are converted into chlorine dioxide and chlorine in high yield.

Suitable reaction conditions may easily be maintained in a-reactor provided with two liquor inlets below the surface of the reaction medium, one or more gasinlets in' or near the bottom of the reactor, and a gas outlettoremove the gaseous products of reaction. One liquor inlet introduces the acid, one the solution of chlorate andchloride, and-'the gas inlets usually admit air, but any other inert gas may be used. Since the molar concentrations of reactants must be kept within reasonable limits, a liquid outlet is also provided.

Acid feed rate is regulated to provide the desired acidity in'the liquid, and feed rate of a solution containing chlorateand chloridein substantially stoichiometric proportions is-regulated'to provide the desired rate of production of the product mixture of chlorine dioxide and chlorine. Alternately, mixing of the chlorate and chloride may'occur. in'situupon separate introduction of the two materials.

The'process of the present invention has an additionaladvantage inits ease of starting or stopping. The production of chlorine dioxide may be stopped by terminatingthe flow of entering solutions while maintaining'the'inert gas stream=orpartial vacuum until most of the chlorinedioxide has been-swept from the reactor.

For restarting, the air or vacuum',.acid; and chlorate- Ychloridestreams'are simply restarted'with no further necessary adjustments. The rate of production of chlorine dioxide may be changed by proportionately changing the rates of flowof the feedstreams.

Thefollowing example 'is illustrative and not limiting of the process of the present invention.

EXAMPLE alyst, 0.02 gram ammonium sulfate, was charged to the flask and the syringes driven slowly to add the reagents over a period of twenty minutes; Reaction temperature was'maintained at 95 C. Air was continuously pulled at 500 milliliters per minute through the solution and atmosphere of the flask to sweep product chlorine dioxide into a potassium iodide-hydrogen chloride scrubber milliliters of 1.134 N HCl and 40 grams KI in one literof water). After 1.3 hours, the contents of the scrubber were diluted to the mark in a two-liter volumetric flask. 100 milliliter samples were titrated with 0.1521 N sodium thiosulfate and 1.007 N sodium hydroxide. From this evaluation it was determined that an '84 percent yield of chlorine dioxide was achieved.

sulfate is present in a concentration of from about 0.1

to about grams per liter of reaction solution.

4. The process of claim 1 wherein said chlorate and chloride are present in substantially stoichiometric quantities.

5. The process of claim 1 wherein said chlorate and chloride are sodium chloride and sodium chlorate.

6. The process of claim 1 wherein said non-oxidizable acid is fluosilicic acid. 

2. The process of claim 1 wherein said reaction is carried out at a temperature of from about 50* C to about 125* C.
 3. The process of claim 1 wherein said ammonium sulfate is preSent in a concentration of from about 0.1 to about 10 grams per liter of reaction solution.
 4. The process of claim 1 wherein said chlorate and chloride are present in substantially stoichiometric quantities.
 5. The process of claim 1 wherein said chlorate and chloride are sodium chloride and sodium chlorate.
 6. The process of claim 1 wherein said non-oxidizable acid is fluosilicic acid. 